U.S. patent application number 11/918717 was filed with the patent office on 2009-02-05 for scroll-type refrigerant compressor.
This patent application is currently assigned to Danfoss Commercial Compressors. Invention is credited to David Genevois, Pierre Ginies, Alexandre Montchamp.
Application Number | 20090035168 11/918717 |
Document ID | / |
Family ID | 35518088 |
Filed Date | 2009-02-05 |
United States Patent
Application |
20090035168 |
Kind Code |
A1 |
Ginies; Pierre ; et
al. |
February 5, 2009 |
Scroll-type refrigerant compressor
Abstract
The invention relates to a scroll-type refrigerant compressor
The inventive compressor comprises: a sealed chamber which is
defined by a ferrule (2) and which contains a suction volume and a
compression volume; and an electric motor which is disposed on the
suction side and which comprises a stator (7) and a rotor (8), the
latter being solidly connected to a drive shaft (26). The stator
(7) is surrounded by an intermediate casing (6) which defines (i)
an annular volume (13) with the moving ferrule (2) of the
compressor and (ii) a chamber (11) containing the coil end of the
motor and facing the compression volume side. The end of the
intermediate casing that faces the side opposite the compression
volume is disposed at the end of the stator facing the side
opposite the compression volume or set back from same. In addition,
means (14) are provided in order to convey at least part of the gas
arriving at the gas inlet in the ferrule into the chamber (11)
containing the coil end.
Inventors: |
Ginies; Pierre; (Sathonay
Village, FR) ; Genevois; David; (Cailloux sur
Fontaine, FR) ; Montchamp; Alexandre; (Moins,
FR) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
Danfoss Commercial
Compressors
Trevoux
FR
|
Family ID: |
35518088 |
Appl. No.: |
11/918717 |
Filed: |
May 23, 2006 |
PCT Filed: |
May 23, 2006 |
PCT NO: |
PCT/FR2006/001176 |
371 Date: |
October 18, 2007 |
Current U.S.
Class: |
418/55.6 ;
418/91; 418/94 |
Current CPC
Class: |
F04C 23/008 20130101;
F04C 28/08 20130101; F04C 29/023 20130101; F04C 29/025 20130101;
F04C 2240/603 20130101; F04C 18/0215 20130101; Y10S 418/01
20130101 |
Class at
Publication: |
418/55.6 ;
418/94; 418/91 |
International
Class: |
F04C 18/04 20060101
F04C018/04; F04C 2/00 20060101 F04C002/00; F04C 29/02 20060101
F04C029/02; F01C 1/04 20060101 F01C001/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 23, 2005 |
FR |
0505153 |
Claims
1. A scroll-type refrigerant compressor comprising: a sealed
enclosure defined by a shell and containing a suction volume and a
compression volume at opposite ends of the enclosure, one on either
side of a body, the shell comprising a refrigerant gas inlet, and
an electric motor on the suction side having a stator and defining
with the shell an annular volume, and a rotor connected to a drive
shaft in the form of a crankshaft, a first end of which drives an
oil pump supplying oil from a sump in the bottom of the enclosure
to a channel formed in the central part of the shaft, the
compression volume containing a stationary volute equipped with a
scroll engaged in a scroll of a moving volute, the two scrolls
defining at least one variable-volume compression chamber, and the
second end of the drive shaft being equipped with a device driving
the moving volute in an orbital movement to compress the suction
gas, wherein the stator is surrounded by an intermediate jacket
defining on the one hand an annular volume with the shell and on
the other hand a chambers which contains the motor winding end and
is directed towards the compression volume side, that end of the
intermediate jacket directed away from the compression volume being
located at that end of the stator which is directed away from the
compression volume or set back therefrom, while means are provided
for conveying at least some of the gas arriving at the gas inlet
formed in the shell, into the chamber containing the winding
end.
2. The compressor as claimed in claim 1, wherein that part of the
motor which is situated on the compression volume side is mounted
inside a tube forming the intermediate jacket which, being mounted
on the body separating the suction and compression volumes, forms a
mounting for the motor, an orifice being formed in the tube,
between the body and the motor, to admit refrigerant gas.
3. The compressor as claimed in claim 1, wherein the body
separating the suction and compression volumes comprises, on the
motor side, a tubular extension forming the intermediate jacket and
serving as a housing and mounting for one end of the motor, an
orifice being formed in the tubular extension of the body to admit
refrigerant gas.
4. The compressor as claimed in claim 1, wherein the motor is
mounted on the shell, and its upper end is covered by a cap forming
the intermediate jacket in which an orifice is formed to admit
refrigerant gas.
5. The compressor as claimed in claim 1, wherein the means for
conveying the refrigerant gas from the inlet orifice formed in the
shell are a tubular sleeve connecting the orifices formed
respectively in the shell and in the intermediate jacket which
defines the chamber containing the winding end.
6. The compressor as claimed in claim 5, wherein the sleeve
comprises a first tubular part mounted on the shell or on the
intermediate jacket covering the motor winding end, and a second
tubular part which slides on the outside of the latter and is
subject to the action of a spring that pushes it towards the part
on which the first tubular part is not mounted.
7. The compressor as claimed in claim 1, wherein the means
conveying the refrigerant gas into the chamber containing the
winding end comprise a by-pass for some of the gas flow to pass
directly into the annular volume between the motor and the
shell.
8. The compressor as claimed in claim 1, wherein there is formed in
the body at least one opening connecting the chamber containing the
winding end to the area containing the drive shaft bearings
situated on the compression volume side.
9. The compressor as claimed in claim 1, wherein it comprises
control means to allow it to be driven by the variable-speed
motor.
10. The compressor as claimed in claim 1, wherein the principal
axis of rotation of the drive shaft is essentially vertical.
11. The compressor as claimed in claim 1, wherein the principal
axis of rotation of the drive shaft is essentially horizontal.
Description
[0001] The present invention relates to a scroll-type refrigerant
compressor.
[0002] A scroll-type compressor (or scroll compressor) comprises a
sealed enclosure defined by a shell containing a suction volume and
a compression volume, the two being separated by a compression
stage, and being situated one at each end of the enclosure. The
shell comprises a refrigerant gas inlet.
[0003] An electric motor is mounted inside the suction volume, with
a stator on the outside, stationary with respect to the shell, and
a rotor in the center, connected to a drive shaft or crankshaft.
The drive shaft contains an off-axis lubrication channel running
all the way along its length and supplied with oil from a sump
situated in the bottom of the enclosure by an oil pump arranged at
a first end of the shaft. The lubrication channel comprises
lubrication orifices for the various guide bearings of the
shaft.
[0004] The compression stage contains a stationary volute equipped
with a scroll engaged in a scroll belonging to a moving volute. The
two scrolls define at least one variable-volume compression
chamber. The second end of the drive shaft is equipped with a crank
which drives the moving volute in an orbital movement to compress
the suction gas.
[0005] Depending on the internal flow configuration of this type of
compressor, the refrigerant gas entering the compressor may pick up
oil. The oil may come from, for example, bearing leaks, or be swept
up off the surface of the oil supplied by the gas, even if speeds
are relatively low and especially if the oil/refrigerant mixture
contained in the oil supply foams up.
[0006] Depending on the operating conditions of this type of
compressor, the amount of oil in the refrigerant gas leaving the
compressor may become excessive. The direct consequence of this
excessive amount of oil in the gas is a loss of heat exchange
efficiency in the heat exchangers situated downstream of the
compressor. This is because oil droplets carried in the gas tend to
deposit on the heat exchangers and form a layer of oil on the
exchangers.
[0007] Moreover, an excessive amount of oil in the gas can also
drain the supply of oil in the sump, which could lead to
destruction of the compressor.
[0008] To alleviate these various situations, systems for
separating the oil/gas mixture already exist.
[0009] One existing oil/gas mixture separating system is disclosed
in document US 2004/0126261.
[0010] In that document, the motor is entirely mounted inside a
tube which, being fixed to the body separating the suction and
compression volumes, serves as a mounting for the motor. The tube
defines on the one hand an annular volume with the shell, and on
the other hand a chamber which contains the motor winding end and
is directed towards the compression volume. A first opening is
formed in the tube, between the body and the motor, to convey gas
arriving through the gas inlet formed in the shell, into the
chamber containing the winding end. A second opening is formed on
the motor side away from the compression volume so that gas can
pass out of the tube into the annular volume between the tube and
the shell.
[0011] From a practical point of view, gas arrives from the outside
and passes directly into the chamber containing the motor winding
end and flows towards the end of the shell furthest from the
compression volume. The flow occurs mostly between the rotor and
the stator, and also at the periphery of the stator, between the
stator and the tube containing the stator. Gas arriving from the
sump area then passes through the second opening and into the
annular volume between the tube and the shell. A deflector is
arranged in front of the second opening to modify the direction and
speed of the gas. These modifications of direction and speed of the
gas cause the oil/gas mixture to separate out, the gas moving
towards the compression stage where it is sucked in, and the oil
draining under gravity into the oil sump.
[0012] In order to be able to operate, this system requires a
sudden change of direction of the gas and an adjustment to the gas
speeds to produce optimal separation of the oil/gas mixture.
[0013] As a result, in variable-capacity operation, this type of
separator suffers from reduced efficiency: at high flow rates,
because of the high speeds of the gases, the oil/gas separation
time is much shorter, which means that particles of oil can be
swept up again into the gas flow after separation.
[0014] Also, the movement of the gas/oil mixture through the outlet
opening or openings of the tube causes the oil/gas mixture to
accelerate locally, which is prejudicial to separation of the
mixture.
[0015] It should be noticed that the lower counterweight of the
motor creates turbulence in the lower end of the tube. This
turbulence reduces the efficiency of separation of the oil/gas
mixture.
[0016] It is therefore an object of the present invention to solve
these problems.
[0017] The technical problem which the invention is intended to
solve is how to provide a scroll-type refrigerant compressor in
which there is efficient oil/gas separation under all conditions of
operation of the compressor.
[0018] To this end, the compressor to which it relates, comprising:
[0019] a sealed enclosure defined by a shell and containing a
suction volume and a compression volume at opposite ends of the
enclosure, one on either side of a body, the shell comprising a
refrigerant gas inlet, and [0020] an electric motor on the suction
side having a stator and defining with the shell an annular volume,
and a rotor connected to a drive shaft in the form of a crankshaft,
a first end of which drives an oil pump supplying oil from a sump
in the bottom of the enclosure to a channel formed in the central
part of the shaft, [0021] the compression volume containing a
stationary volute equipped with a scroll engaged in a scroll of a
moving volute, the two scrolls defining at least one
variable-volume compression chamber, and [0022] the second end of
the drive shaft being equipped with a device driving the moving
volute in an orbital movement to compress the suction gas, is
characterized in that the stator is surrounded by an intermediate
jacket defining on the one hand an annular volume with the shell
and on the other hand a chamber which contains the motor winding
end and is directed towards the compression volume side, that end
of the intermediate jacket directed away from the compression
volume being located at that end of the stator which is directed
away from the compression volume or set back therefrom, while means
are provided for conveying at least some of the gas arriving at the
gas inlet formed in the shell, into the chamber containing the
winding end.
[0023] The gas flows around the motor in the following manner: at
least some of the gas enters the chamber containing the motor
winding end and re-emerges, after passing between the rotor and the
stator, at the winding end furthest from the compression volume.
Lubricating oil-laden gas flowing in contact with the motor
encourages the return of this lubricating oil to the oil sump, and
promotes cooling of the motor. After this, the gas flow diffuses
into a large annular volume between the oil sump and the winding
end furthest from the compression volume. The gas flow then moves
into the annular volume between the stator and the shell, and the
annular volume between the shell and the chamber containing the
winding end, before reaching the compression stage, into which it
is sucked.
[0024] While the gas is flowing through the motor airgap, it is
flowing through a small volume, the effect of which is to increase
the gas flow speed. Then, as the gas leaves the motor airgap it
diffuses suddenly into a very large annular volume. This sudden
change to the cross section of the gas flow causes a large drop in
the speed of the gas flow.
[0025] Furthermore, the diffusion of the gas into the annular
volume between the oil sump and the end of the motor furthest from
the compression volume also involves a change in the direction of
the gas flow.
[0026] The effect of these changes of speed and direction is to
efficiently separate the oil/gas mixture, the gas flowing on
towards the compression stage and the oil draining under gravity
into the oil supply.
[0027] Additionally, because of the large size of the annular
volume between the oil sump and the motor end furthest from the
compression volume, the speeds reached by the gas as it passes out
of the motor will remain slow even when the compressor is being
used in variable capacity.
[0028] The oil/gas separation will therefore continue to be
efficient under all conditions of operation of the compressor.
[0029] It should be observed that as the gas carries away the heat
from the motor, it will heat up the shell on its way through the
annular space. Some of the thermal losses of the motor can thus be
discharged directly through the outside of the compressor, reducing
the overheating at the volute intake, which reduces the performance
of the compressor.
[0030] Lastly, the droplets of lubricating oil moving over the
motor on their way back to the sump cool the motor and discharge
the thermal losses through the compressor sump. Since the oil is
hotter, it contains less dissolved refrigerant fluid and maintains
greater lubricating power.
[0031] In general terms, the overheating at the suction into the
volutes is lowered, and because of the potential use of the by-pass
the total pressure loss between the suction connection and the
volute suction will be lower and beneficial to the efficiency of
the compressor.
[0032] In a first embodiment of this compressor, that part of the
motor which is situated on the compression volume side is mounted
inside a tube forming the intermediate jacket which, being mounted
on the body separating the suction and compression volumes, forms a
mounting for the motor, an orifice being formed in the tube,
between the body and the motor, to admit refrigerant gas.
[0033] In another embodiment of this compressor, the body
separating the suction and compression volumes comprises, on the
motor side, a tubular extension forming the intermediate jacket and
serving as a housing and mounting for one end of the motor, an
orifice being formed in the tubular extension of the body to admit
refrigerant gas.
[0034] In a third embodiment of this compressor, the motor is
mounted on the shell, and its upper end is covered by a cap forming
the intermediate jacket in which an orifice is formed to admit
refrigerant gas.
[0035] In accordance with one feature of the invention, the means
for conveying the refrigerant gas from the inlet orifice formed in
the shell are a tubular sleeve connecting the orifices formed
respectively in the shell and in the intermediate jacket which
defines the chamber containing the winding end.
[0036] The sleeve advantageously comprises a first tubular part
mounted on the shell or on the intermediate jacket covering the end
of the motor, and a second tubular part which slides on the outside
of the latter and is subject to the action of a spring that pushes
it towards the part on which the first tubular part is not
mounted.
[0037] This arrangement makes it possible to absorb differential
expansions between the different components, and tolerances between
parts and tolerances in the assembly process.
[0038] In accordance with one feature of the invention, the means
conveying the refrigerant gas into the chamber containing the
winding end comprise a by-pass for some of the gas flow to pass
directly into the annular volume between the motor and the
shell.
[0039] The by-pass is also calculated so that the gas flow rate
passing through the motor is equal to the flow rate necessary to
cool the motor and minimizes pressure loss.
[0040] In accordance with one feature of the invention, there is
formed in the body at least one opening connecting the chamber
containing the winding end to the area containing the drive shaft
bearings situated on the compression volume side.
[0041] The compressor advantageously comprises control means to
allow it to be driven by the variable-speed motor.
[0042] The principal axis of rotation of the drive shaft may be
vertical, or inclined in a position between horizontal and
vertical.
[0043] The invention will be clearly understood from the following
description, which refers to the accompanying schematic drawing
showing, by way of non-restrictive examples, a number of
embodiments of this compressor.
[0044] FIG. 1 is a view in longitudinal cross section through a
first compressor.
[0045] FIG. 2 is a view in transverse cross section through the
electric motor and through the tube surrounding it.
[0046] FIG. 3 is a view in longitudinal cross section through a
second compressor in which the body possesses an extension in the
direction of the motor.
[0047] FIG. 4 is a view in longitudinal cross section through a
third compressor.
[0048] FIGS. 5 and 6 are two partial views, in cross section,
through two methods of supplying refrigerant fluid to the motor
compartment.
[0049] FIG. 7 is a schematic view of another compressor.
[0050] In the following description, recurring components are
denoted by the same references in all embodiments.
[0051] FIG. 1 shows a scroll refrigerant compressor occupying a
vertical position. However, the compressor according to the
invention can be placed in an inclined position, or a horizontal
position, without modifying its structure.
[0052] The compressor shown in FIG. 1 comprises a sealed enclosure
defined by a shell 2 whose upper and lower ends are closed by a
cover 3 and a base 4, respectively. The intermediate part of the
compressor is occupied by a body 5 that defines two volumes, a
suction volume underneath the body 5, and a compression volume
above. Mounted on the body is a tube 6, and inside the tube is
mounted an electric motor comprising a stator 7 with a rotor 8 in
the center. The tube 6 may for example be crimped to the stator to
support the motor. The lower end of the tube 6 is situated at the
lower end of the stator 7.
[0053] An orifice 10 is formed in the shell 2 and connected to a
connector 12 to admit gas into the compressor. This connector 12
opens into an annular volume 13 between the shell 2 and the tube 6
containing the motor, at the top of the motor.
[0054] The connector 12 is extended through the annular volume 13
by a sleeve 14 which passes through this annular space and opens
into an upper chamber 11, defined by the tube 6, which contains the
motor winding end. There is a by-pass opening 15 in the sleeve 14
where it passes through the annular volume 13.
[0055] The body 5 serves as a mounting for the gas compression
stage 16. This compression stage comprises a stationary volute 17
equipped with a downward-facing stationary scroll 18, and a moving
volute 19 equipped with an upward-facing scroll 20. The two scrolls
18 and 20 of the two volutes fit one inside the other to create
variable-volume compression chambers 22. Gas enters from the
exterior: the compression chambers 22 have a variable volume which
decreases from the outside in as the moving volute 19 moves
relative to the stationary volute 17, and the compressed gas
escapes from the center of the volutes through an opening 23
leading into a chamber 24 from which it is discharged via a
connector 25.
[0056] The rotor 8 is coupled to a shaft 26 whose upper end is
off-axis, like a crankshaft. This upper end is engaged in a bush
part 27 of the moving volute 19. As it is turned by the motor, the
shaft 26 drives the moving volute, which is guided by a connecting
piece 28 relative to the stationary volute 17, in an orbital
movement.
[0057] The shaft 26 is guided relative to the other parts by a
lower bearing 29 formed in a centering piece 9 mounted on the shell
2, then via an intermediate bearing 30 formed in the body 5, and
then via an upper bearing 32 formed between the shaft 26 and the
bush 27. The volume containing the upper bearing 32 communicates
with the chamber 11 through openings 21 in the body 5.
[0058] The base 4 defines a sump 31 containing the oil, the oil
level being shown by reference 33. The oil bath bathes the end of
the pump intake channel 34, which supplies lubricating oil to the
various bearings along a channel 35 which is inclined with respect
to the shaft axis and which leads to the shaft end adjacent to the
moving volute 19 as well as through orifices 36 level with the
bearings, for their lubrication. At the top, lubricating oil can
return to the sump by trickling through the openings 21 in the body
5 and through interstices running through the motor, allowing the
oil leaking from the bearings 30, 32 and from the moving volute 19
to trickle down toward the motor, thereby increasing the amount of
oil passing through it.
[0059] In FIG. 1, large arrows represent gas flow, small arrows
represent oil flow.
[0060] In the embodiment depicted in the drawing, the shaft 26 also
includes an oil return channel 37, which may be parallel to or
inclined with respect to the shaft axis, with one open end at the
moving volute shaft end, in the center of the shaft, and the other
open end in the peripheral wall of the shaft, at the bottom of the
motor.
[0061] The return channel 37 advantageously communicates with the
lubrication channel 35 through a number of transverse orifices 39
to promote degassing of the oil supplying the bearings.
[0062] Operation of this compressor is as follows: refrigerant gas
carrying oil and potentially liquid particles arrives through the
connector 12. A large part of the gas flow passes through the
sleeve 14 into the volume defined by the tube 6 above the motor.
Another part of the flow passes through the by-pass channel 15 into
the annular volume 13 to flow directly towards the compression
stage 16. Gas arriving in the volume above the motor mixes with the
lubricating oil flowing towards the lower bearing 29, particularly
from the upper bearing 32 and from the intermediate bearing 30. The
mixture of gas and lubricating oil travels downward through the
motor, carrying away the thermal losses of the motor. Most of it
passes through a gap 43 between the rotor and the stator, and
through gaps 44 between the stator and the tube 6 in positions
where there are flats on the stator, as shown in FIG. 2. The mixed
flow passing down through the motor arrives at the bottom of the
motor where the flow of oil from the lower bearing is added to it.
The gas/oil mixture then diffuses into a large annular volume 40
situated between the centering piece 9 and the motor. The changes
of direction and differences of speed cause the oil to be separated
from the gaseous flow and fall back into the sump 31. The gaseous
flow then travels up the annular volume 13 toward the compression
stage 16. The separation of the gas and the oil continues during
the journey up through the annular volume due to gravity and/or due
to the controlled gas speeds and a calculated separation time.
[0063] The provision of an oil return channel 37 allows a high flow
rate of oil to be removed, besides ensuring that it returns to the
sump, irrespective of the flow rate applied by the pump and the
speed of rotation. A large lubricating oil return flow rate is also
a favorable factor in cooling the bottom of the motor.
[0064] The fact that the oil flow rate through the motor can be
augmented by the flow rate via the openings 21 allows better
cooling of the motor.
[0065] With this structure, and as indicated earlier, overheating
of the refrigerant gas entering the volutes is lowered and the
pressure loss is reduced. This structure is therefore particularly
suitable for constructing high-efficiency compressors for
refrigeration, air conditioning and variable speed.
[0066] FIG. 3 shows an alternative embodiment of the compressor
seen in FIG. 1, in which recurring parts are denoted by the same
references as before. In this compressor, the motor is not mounted
on a tube. In this case, the body 5 comprises a downward tubular
extension 45 which grips the upper end of the motor, for which it
serves as a mounting, and which has an orifice 46 for the intake of
gas through a sleeve 14.
[0067] In the embodiment shown in FIG. 4, the motor is mounted not
on the body 5, but directly on the shell 2 via a collar 47 which
encircles the stator and is connected to the shell 2 by spokes 48.
In a case like this, the upper end of the motor is covered by a cap
49 defining the chamber 11, which is supplied with refrigerant gas
through a sleeve 14 via an orifice 50. A space 15a between the
sleeve 14 and the orifice 50 of the cap 49 forms a by-pass,
allowing part of the fluid flow to enter the annular space 13
directly. In this form, the cap 49 may advantageously form a
collector 49a of lubricating oil coming from the upper bearings of
the crankshaft and allow oil to pass between the shaft and the
center of the cap 49b: this lubricating oil then mixes with the
refrigerant gas in the volume defined by the cap.
[0068] FIGS. 5 and 6 show two embodiments of the sleeve supplying
gas to the chamber 11 containing the motor winding end. In FIGS. 5
and 6 the motor is shown schematically and indicated by references
7 and 8. FIGS. 5 and 6 show the sleeve used in the device of FIGS.
1 and 2, though this arrangement can be transferred to the
embodiments shown in FIGS. 3 and 4. In the case of FIG. 5, the
sleeve 14 comprises a tubular part 14a mounted on the tube 6, while
there slides around it a tubular part 14b acted on by a spring 52
designed to push it against the wall of the shell 2.
[0069] FIG. 6 is an opposite arrangement: in this case the tubular
part 14a is fixed to the shell 2 and guides the part 14b which is
acted upon by the spring 52 to push against the outer wall of the
tube 6.
[0070] FIG. 7 shows an alternative embodiment of the compressor
according to the invention, in which the principal axis of rotation
of the drive shaft is essentially horizontal.
[0071] As a result of this position, the pump 34 is not immersed
directly into the oil bath but is provided with a suction tube 54
whose end is in the oil, and the discharge tube 25 is in the center
of the cover 3.
[0072] It goes without saying the invention is not limited to the
embodiments of this compressor described above by way of examples:
on the contrary it encompasses all alternative embodiments thereof.
As a particular example, the compressor does not have to be
vertical but can be inclined without thereby departing from the
scope of the invention.
* * * * *